The objective of our current program is to understand the mechanisms of growth control of normal and malignant cells. The program is organized in four parts: Tumor virology: These studies are aimed at understanding the genetic organization of RNA and DNA tumor viruses and the effects of viral gene expression of cell growth regulation. The objective is to define the nature and control of molecules that affect cell growth regulation. 2. Cell surface immunology and biochemistry: We are using immunological, biochemical and genetic techniques to study the nature, function and regulation of selected molecules on normal and malignant lymphocytes. These studies are aimed at understanding how surface molecules in general, and tumor-associated molecules in particular, are controlled, and at understanding the properties of cells of the immune system whose function it is to recognize and kill tumor cells. 3. Mammary differentiation: We are studying the differentiation of the mammary gland in rats and mice, the growth control of mammary epithelial cells, mechanisms of carcinogenesis and the properties of mammary cancer cells. The objective is to develop approaches toward prevention and treatment of breast cancer. 4. Gene expression: We are studying the genomic organization and control of expression of genes expressed in normal and malignant cells. The objective is to develop approaches toward controlling the growth of tumor cells.